1. Field of the Invention
The present invention relates to imprint lithography templates suitable for use in micro-fabrication of structures. The compliant template herein described has particular utility in pattern transfer onto non-planar surfaces.
2. Description of the Related Art
Micro-fabrication involves the fabrication of very small structures, e.g., having features on the order of micrometers or smaller. One industry that has been driving the fabrication of increasingly smaller structures is the electronics industry. As electronic devices have become smaller and faster, the integrated circuits that drive them have necessarily become smaller.
Lithographic techniques are usually employed in the manufacture of integrated circuits. Typically, these lithographic techniques include applying photosensitive materials to a semiconductor substrate. These photosensitive materials, commonly referred to as “resist,” are selectively exposed to a form of radiation. An exposure tool and a photomask are often used to obtain the desired selective exposure. Such exposure changes the solubility of the resist such that the photomask's pattern is formed in the resist following a development process to remove the soluble resist.
Historically, exposure tools have been optical systems. However, optical systems are limited in their ability to resolve very small features. For example, the equation for resolution, where λ is wavelength and NA is numerical aperture, is as follows:RES=k1λ/NAThe resolution of ever-smaller features requires a reduction of wavelength, an increase in numerical aperture, or both. Of course, reducing wavelength significantly below 248 nm, currently used in deep UV lithography, is not trivial. Further, increasing numerical aperture results in a significant depth of focus loss, as shown in the following equation, where again λ is wavelength and NA is numerical aperture:DOF=k2λ/(NA)2
Accordingly, optical lithography systems capable of printing microstructures may require a depth of focus so small as to be intolerant of slight wafer non-planarity, which commonly results from normal process variation. Therefore, due to slight wafer non-planarity, as well as the limitations of wavelength reduction, optical lithography is limited in its ability to print the sub-100 nm features that will be required for the manufacture of future integrated circuits.
Imprint lithography is capable of manufacturably producing sub-100 nm features. Several imprint lithography techniques have been investigated as low cost, high volume manufacturing alternatives to conventional photolithography for high-resolution patterning. In this emergent technology, a relief image in a template is used to replicate a surface relief into a polymerizable material arranged upon the surface of a substrate. The template makes mechanical contact with the material arranged upon the substrate, and the material is subjected to conditions to solidify and/or to polymerize the same such that a relief structure complimentary to that of the template is formed on the substrate. The material may be solidified or polymerized by, for example, heat or light. Such patterning and polymerization techniques may be referred to as thermal imprint lithography or ultraviolet (‘UV’) imprint lithography, respectively. Typical substrates may include semiconductors, dielectric materials, magnetic, or optoelectronic materials. Unlike optical lithography, resolution of imprint lithography is not limited by wavelength. However, imprint lithography may be limited by the ability to create high-resolution templates and the ability to transfer relief images on such templates. Consequently, templates with an ability to conform to non-planar surfaces are desired. Further, because lithography is typically the single largest component of integrated circuit fabrication cost, a template that may be used interchangeably for either UV or thermal imprinting is desired. It is desired, therefore, to provide an improved template for use in micro-fabrication.